This application claims the priority of German Patent Application, Serial No. 199 36 869.4, filed Aug. 5, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a coaxial overvoltage protector.
German Pat. No. DE 195 20 974 A1 describes an overvoltage protector having a coaxial transmission line with an inner conductor and an outer conductor, and a xcex/4 short-circuit line with an inner conductor radially branching off the inner conductor of the coaxial transmission line. The inner conductor of the xcex/4 short-circuit line is guided in insulated manner through a wall of the outer conductor of the coaxial transmission line and has a portion, which is received in a chamber of the outer conductor, and has one end electrically contacted with the outer conductor of the coaxial transmission line. The chamber in the outer conductor for accommodating the portion of the inner conductor of the xcex/4 short-circuit line is configured as coaxial annular space, so that the portion of the inner conductor of the xcex/4 short-circuit line extends in a radial plane of the coaxial transmission line. As a consequence of this configuration, the overvoltage protector has a comparably great diameter. The annular space can be made only by a complicated material removal process of an accordingly massive blank, requires a flanged ring to form one of both walls of the annular space which extend in a radial plane, and the provision of an outer ring for sealing off the annular space against the outside. Of course, suitable seals must also be provided between all these components.
It is thus an object of the present invention to provide an improved overvoltage protector, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved overvoltage protector which is simple in structure and yet reliable in operation.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a coaxial transmission line defining an axis and having an inner conductor and an outer conductor; and a xcex/4 short-circuit line having an inner conductor radially branching off the inner conductor of the coaxial transmission line and electrically contacted with the outer conductor of the coaxial transmission line, with the inner conductor of the xcex/4 short-circuit line being guided in insulated manner through a wall of the outer conductor of the coaxial transmission line into a chamber of the outer conductor so as to define a portion which is received in the chamber of the outer conductor, whereby the portion of the inner conductor of the xcex/4 short-circuit line is oriented at least approximately in a plane which is parallel to the axis of the coaxial transmission line.
By so constructing an overvoltage protector in accordance with the present invention, the chamber can be configured, so to speak, as an attachment upon the outer conductor of the coaxial transmission line, having a flat bottom and a flat lid. As a consequence, the outer dimensions are reduced and significant savings with respect to manufacturing costs are realized. In addition, the size of the chamber can be more easily suited to the length of the inner conductor of the xcex/4 short-circuit line. As is generally known in the art, the length of the inner conductor of the xcex/4 short-circuit line is directly governed by the nominal frequency for which the overvoltage protector is dimensioned.
According to another feature of the present invention, the portion of the inner conductor of the xcex/4 short-circuit line may have a substantially ring-shaped configuration around an axis which is substantially perpendicular to the axis of the coaxial transmission line, This configuration is especially space-saving and suitable for nominal frequencies of few 100 MHz.
According to another feature of the present invention, the outer conductor of the coaxial transmission line can be configured with a channel in the chamber, with the portion of the inner conductor of the short-circuit line extending in the channel. In this manner, a compact structure or relatively low nominal frequencies, i.e. situations when the inner conductor of the xcex/4 short-circuit line is relatively long, can be implemented. The channel may be configured in the form of a spiral or a coil winding so as to exhibit a length which exceeds the perimeter of the chamber. The walls of the channel may be metal, in particular when the portion of the short-circuit line is configured as band-shaped line. Of course, the outwardly directed portion of the short-circuit line may be made of any other suitable line construction, e.g. as strip line or as microstrip.
According to still another feature of the present invention, the outer conductor is formed by a metal body which forms the chamber for accommodating the portion of the inner conductor of the xcex/4 short-circuit line.